SUMMIT: SUMmer Mechatronics Institute for Teachers 2007
Compression Testing Apparatus
by
Sabah Ayoub & Lindrick Outerbridge
Professor Vikran Kapila
OUTLINE
1- Abstract
2- Introduction
3- Background information
1- type of bridges
2- forces acting on bridges
5-Material used
6-Experiment
3- The device
4- Electrical circuit
7-How its work
8-Computer program
9-Results
10-Conclusion
11Future work
12-Activities
13-Curriculum correlation: standards
1- Physics
2- Technology
3- Interdisciplinary
14- Acknowledgements
15- References
1-Abstract
The intent of this project is to provide students with a visual demonstration of material tested for compression. This demonstration will be used in technology and physical science classes. The use of electrical part, mechanical parts and computer programming will also provide more interdisciplinary lessons.
2-Introduction
Who among us, really, hasn't crossed a bridge and at least paused over the disconcerting possibility that the structure might collapse into free fall?
“A 600-foot section of an interstate bridge over the Arkansas River collapsed on May 26, 2007 when one of two barges going north on the river rammed a pylon. About a dozen vehicles plunged into the river. Five people were rescued from the water, but authorities are certain that there were fatalities.”
“Late July 2007, a 40-year-old interstate highway bridge collapsed in Minneapolis, plunging rush-hour traffic into the Mississippi River 60 feet below.”
Truss bridges such as the one in Minneapolis, whose pillars carry loads by tension and compression, long have been the workhorses. They were invented in America to span wide waterways, the Mississippi in particular, and this is the big question today in Minneapolis. Why did the bridge collapse?
While bridge collapses are rare, they remain spectacular and have a lasting impact on people' minds.
As a minimum, the goal is to break that chain of failures by conducting a proactive research program that provides solutions that can be implemented prior to the catastrophic failure. The key to avoid future horrific circumstances will be the use of advanced or enhanced materials, inspection technology, design procedures, construction methods, operational practices, maintenance and rehabilitation technology, and management techniques. We must use technology that permits to test, during the design stage of the bridge, all beams and columns susceptible to keep the bridge safe and stable. The challenge to develop and implement this technology must be undertaken in partnership with the entire highway community -- government at all levels, universities, highway users, the construction industry, and heavy vehicle manufacturers.
In our summer project with Summit at Polytechnic Institute, as a team, we have opted for an apparatus that will detect and display the maximum force structural material undergoes. Selection for this project falls well into our study scope, as we teach students physics and technology. Both have agreed this venture will benefit our student population back in our schools.
The compression apparatus determines the equilibrium force, which is the maximum load a structural element as a beam or a column can sustain. Loads may include the weight of truck and cars in motion, force of the wind, weight of snow, our compression apparatus is operated in association with a two platen parts which one can move relative to one another. The compression apparatus is formed of at least one compression units having a working chamber and a working element which can move in it.
3-- Background information
They are many types of bridges all over the world. What make them different will depend on their purpose, location, environment, length of span, material they are made of and their cost.
The most common bridges are:
1- Type of bridges
Arch bridges are the earliest one
Beam bridges are the simplest one.
Cable bridges are used for medium span.
Used to span great distance
They can open to allow boat to go through
Have the longest span distance
2- Forces acting on bridges:
When designing and constructing a bridge, engineers have to consider many factors. They need to know which material and structure is best for a stable bridge? Many forces act on a bridge. The two most important one are tension and compression bridges.
Compression is a force that acts to compress or shorten the object it is acting on.
Tension is the force that acts to extend or expend the object it is acting on
Tension
Compression
Material can have both tension and compression applied at the same time .A good examples of these are bridges.
In any static structure such as bridges they will be forces acting on it at any point. These forces need to be in equilibrium.
The blue arrows represent tension
The red arrows represent compression
The green arrows represent force of gravity
The structural members of a bridge will react to those acting on them by producing internal forces. They do this by deflecting until the forces they generate balance the one applied on them. If a member reaches its limit of strength before the necessary force is attained, it will bend, snap, twist or break. It is the task of the bridge designer to analyze and study these forces in order to avoid buckling or snapping. Buckling is what happens when the force of compression overcomes an object's ability to handle compression, and snapping is what happens when the force of tension overcomes an object's ability to handle tension
Minneapolis Mississippi Bridge I-35w
The bridge collapse during Minneapolis Rush hour on Wednesday 08-01-07 has raised questions about structural problem
BEFORE
AFTER
Our project is to build a device (compression testing apparatus) that will simulate how materials are tested for their ability to resist compression.
4 Material used;
1- flexi Force:
Flexi force sensor and the capacitor are the
basic tools in this project.
Flexi Force measures compression exerted versus resistance. The resistance of flexi force is proportional to weight .
2-Board of education (BOE)
The board of education supplies a regulated +5volts (Vdd) and ground (Vss) as well as a small breadboard for circuit and connector to 16 pins.
3- Piezo Speaker: used as a signal to stat a program
4-motor: used to move the movable piston up a down
5-push button: used to start and stop the program
6-capacitor: is connected to the flexi force
7- Pololu motor micro controller: can independently set motor to go forward or backward.
8-Parallax serial LCD: provides basic text wrapping on the display
5-Experiment
1-The device
At equilibrium:
Force F = Force Fr IF FORCE F> REACTION FORCE Fr the object will buckle.
Compression testing
Apparatus model
Design
2--Electrical circuit
6- Computer Program
' Compression Testing Machine - CompressionMachine.bs2
' Progrsm Listing
' Programmers: Lindrick Outerbridge
' Sabah
' {$STAMP BS2}
' {$PBASIC 2.5}
' -----[ Revision History ]------
' 8/1/07
' 8/9/07 VFD Display shows realtime force values. Shows greatest value at the end.
' -----[ Declarations ]------
rawForce VAR Word ' Stores raw output
sensorPin CON 1 ' Flexiforce sensor circuit
calibration CON 6000 ' Calibration raw Flexiforce equivalent to 1 kg mass
calibtimesgrav CON 58860 ' calibration times 9.81 gravity constant
counter VAR Word
ForceInteger VAR Byte
ForceDecimal VAR Byte
speed VAR Byte ' DC motor speed
Force VAR Byte
LargestForce VAR Byte
LFInteger VAR Byte
LFDecimal VAR Byte
' -----[ I/O Definitions ]------
VFD PIN 5 'VFD Serial I/O PIN
' *********** CHECK YOUR WIRING BEFORE POWERING UP THE VFD ***********
' -----[ Constants ]------
Baud CON 6 ' 38.4 Kbps (BS2)
' These are constants for common control characters on the display.
' Remember, some are already defined in the editor, like CR and LF.
BS CON $08 ' Back Space
HT CON $09 ' Horizontal Tab
HOM CON $0B ' Home Position
CLR CON $0C ' Display Clear
' -----[ Variables ]------
index VAR Byte ' Index Variable
' -----[ Initialization ]------
HIGH VFD ' Initialize I/O Pin
PAUSE 200 ' Allow Time To Settle
' This command resets the display settings to deafult values, but the input
' buffer is not affected (contents remain).
SEROUT VFD, Baud, [$1B, $40, $0C] ' Initialize Display
PAUSE 200 ' Allow Time To Settle
' You need to set this if you plan to write to the non-visible display
' memory. Write Screen Mode Select: 0=Display Screen, 1=All Screen
SEROUT VFD, Baud, [$1F, $28, $77, $10, $01]
' This digit is the one to change ^^
' -----[ Program Code ]------
Main:
SEROUT VFD, Baud, ["Compression Test", CR, LF, " Apparatus"] ' Title Screen
PAUSE 3000
SEROUT VFD, Baud, [CLR] ' Clear The Display
SEROUT VFD, Baud, ["Outerbridge, L.", CR, LF, " Sabah Ayoub"]
PAUSE 2000
DO
GOSUB Display_On_Off ' Do Display On/Off Demo
GOSUB Wait_For_Start ' Do Wait for Button Press
LOOP ' Loop Forever
' -----[ Subroutines ]------
Display_On_Off:
SEROUT VFD, Baud, [CLR] ' Clear The Display
SEROUT VFD, Baud, [" SUMMIT 2007", CR, LF, " PolyTechnic U."]
PAUSE 2000
RETURN
' ------
Wait_For_Start:
' Prepare motor for operation
HIGH 2 ' take serial line high
LOW 3 ' reset motor controller
HIGH 3
PAUSE 100 ' motor controller startup time
SEROUT VFD, Baud, [CLR] ' Clear The Display
SEROUT VFD, Baud, ["Model CTA-OA-07 ", CR, LF, "START ADJUST"]
LargestForce = 0
DO
LOOP UNTIL IN0 = 1 OR IN4 = 1 ' wait for any button press
IF IN0 = 1 THEN ' Start compression testing
GOSUB Start_Machine
RETURN
ENDIF
IF IN4 = 1 THEN ' Config mode to adjust height
SEROUT VFD, Baud, [CLR] ' Clear The Display
SEROUT VFD, Baud, [" Load Length", CR, LF, "LOWER RAISE"]
PAUSE 100
DO
LOOP UNTIL IN0 = 1 OR IN4 = 1
FREQOUT 6, 200, 2000 ' Beep sound
IF IN0 = 1 THEN ' move down until black button is pressed again
FREQOUT 6, 200, 2000 ' Beep sound
SEROUT VFD, Baud, [CLR] ' Clear The Display
SEROUT VFD, Baud, [" Caution", CR, LF, "Lowering Plates"]
DO
SEROUT 2,84,[$80, 0, 1,127]
PAUSE 20
LOOP UNTIL IN0 = 1
FREQOUT 6, 200, 2000 ' Beep sound
ENDIF
IF IN4 = 1 THEN ' move up until red button is pressed again
FREQOUT 6, 200, 2000 ' Beep sound
SEROUT VFD, Baud, [CLR] ' Clear The Display
SEROUT VFD, Baud, [" Caution", CR, LF, " Raising Plates"]
DO
SEROUT 2,84,[$80, 0, 0,127]
PAUSE 20
LOOP UNTIL IN4 = 1
FREQOUT 6, 200, 2000 ' Beep sound
ENDIF
RETURN
ENDIF
DEBUG CLS
RETURN
' ------
Start_Machine:
LargestForce = 1
' Starting Sound - a beep
FREQOUT 6, 200, 2000
' Run Motor
HIGH 2 ' take serial line high
LOW 3 ' reset motor controller
HIGH 3
PAUSE 100 ' motor controller startup time
' Apparatus is engaged - Caution!
SEROUT VFD, Baud, [CLR] ' Clear The Display
SEROUT VFD, Baud, ["Keep Clear", CR, LF, "At All Times"]
DO
' Read FlexiForce Sensor
HIGH sensorPin ' Discharge the capacitor
PAUSE 2
RCTIME sensorPin,1,rawForce ' Measure RC charge time
DEBUG "Flexiforce raw output = ", DEC rawForce,CR
SEROUT VFD, Baud, [CLR] ' Clear The Display
Force = calibtimesgrav / rawforce
ForceInteger = Force
ForceDecimal = (calibtimesgrav) // rawforce
IF ForceInteger > LargestForce THEN
DEBUG "hello"
LargestForce = ForceInteger
LFInteger = ForceInteger
LFDecimal = ForceDecimal
ENDIF
SEROUT VFD,Baud, ["Specimen Testing:",CR,LF]
SEROUT VFD, Baud, [DEC3 ForceInteger,".", DEC2 ForceDecimal,"N"]
SEROUT 2,84,[$80, 0, 1,50]
PAUSE 20
LOOP UNTIL IN0 = 1
FREQOUT 6, 200, 2000 ' Beep sound
' Slow motor down to complete stop
FOR speed = 127 TO 0
SEROUT 2,84,[$80, 0, 0,speed]
PAUSE 20
NEXT
SEROUT VFD, Baud, [CLR]
SEROUT VFD,Baud, ["Max. Strength:",CR,LF]
SEROUT VFD, Baud, [DEC3 LFInteger,".", DEC2 LFDecimal,"N"]
PAUSE 5000
DO
LOOP UNTIL (IN0 = 1 OR IN4 = 1)
FREQOUT 6, 200, 2000 ' Beep sound
RETURN
' ------
7-How it works:
The flexi force whish is connected to a capacitor acts like a resistor. When the sensor is unloaded its resistance is very high (the rctime will be low). When a force is applied to the sensor, its resistance decreases (the rctime will be).
The computer will read the input from the flexi force as raw number. A command in the programming will change this raw number into a Newton. Using a the rctime of a known mass (in our case 1 Kg)
The black push button starts the motor that will rotate forward turning the screw the pushes the piston down.
The red push button will end the program and will make the motor rotate backward making the piston go up.
The motor that is controlled by the microcontroller will increase the compression on the load (object tested) until the object buckles.
The result (the highest compression) is displayed in the LCD
8-Results
Test Number / Size / Length / Compressive Strength(mm) / (cm) / (N)
C1 / 10 x 10 / 5 / 79.63
C1 / 10 x 10 / 5 / 78.48
C1 / 10 x 10 / 5 / 81.54
C2 / 10 x 10 / 10 / 70.71
C2 / 10 x 10 / 10 / 77.84
C2 / 10 x 10 / 10 / 76.72
C3 / 10 x 10 / 15 / 60.2
C3 / 10 x 10 / 15 / 62.15
C3 / 10 x 10 / 15 / 58.12
C4 / 6 x 10 / 5
C4 / 6 x 10 / 5
C4 / 6 x 10 / 5
C5 / 6 x 10 / 10 / 39.55
C5 / 6 x 10 / 10
C5 / 6 x 10 / 10
C6 / 6 x 10 / 15
C6 / 6 x 10 / 15
C6 / 6 x 10 / 15
Plastic Straws / Radius / Length
cm / cm
circular / 0.5 / 5 / 155.14
circular / 0.5 / 6 / 96.4
circular / 0.5 / 7 / 85.38
circular / 0.5 / 12 / 82.42
Triangle / 6 / 32.7
Triangle / 12 / 11.97
Wood / Radius / Length
circular / 0.5 / 6 / 52.4
Triangle / 6 / 36.5
9- Conclusion
Throughout this project, our goal was to provide students with a visual demonstration of the procedure engineers use to test materials for their strength using a compressor. Our compression testing apparatus is a smaller scale model that operates and replicates what actual compressors run and test in the industry standards. We believe this experiment conducted in our school lab will confer our students with clear idea of the actual procedures, and hence will help them make decisions and planning regarding their what-about their would be exposed later if they were to opt for this rapidly growing engineering field.
10--Future work
Design a device that will test how much an object can extend (measure tension) and see if there is any type of relation between the compression and the tension of a same object
11-Activities
1- Explain that when forces on an object are balanced, the motion of the object does not change.
2- Identify all the forces acting on a single object.
3- Determine what factors need to be considered in building stable object.
4- Determine what structure is more suitable for building a stable bridge.
5- Compare and contract the pros and the cons of various bridge building materials.
6- Draw a graph.
7- Newton third law of motion : for every action there is an equal and opposite reaction
8- Analyze data
12-Curriculum Correlation: NY State standards
1-PHYSICS
STANDARD 4: investigate the use of common forces (push and pull) on objects.
Standards 5: matter is made up of particles whose properties determine the observable characteristics of matter and its reactivity
2--Technology:
Standard 5: students will apply technology knowledge and skills to design, construct, use and evaluate product and systems to satisfy human and environmental needs
3-Interdisciplinary
Standard 6: students will understand the relationships and common themes that connect mathematics, science and technology.
Standard 7: student will use the knowledge of thinking skill of mathematics, science and technology to address real life problems and make informed decisions.
ACKNOWLEDGEMENTS
We would like to thank the following persons for their guidance throughout this project
Sang Hoon (Nathan)LEE
Anshuman Panda
Padmini Vijayakumar
Kwokkei(Keith)Ching
Jared Frank
Billy Mark
Shing Lik Wong
and special thanks for Danial Remiszewski for his support and patience and Professor Vikram Kapila for his overall assistance
References
1- 32.brinkster.com
2- Glenbrook.k12.il.us/GBSSCI/physic.
3-
4- Parallax.com
5-
6-
7- What is a microcontroller .by Andy Lindsy. Version 2.2
8- Basic stamp syntax and reference manual version 2.2
9-
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